I've communicated with ebikes.ca and they've been quick to respond, knowlegable and technically proficient. They recommended a kit based on my requirements. The forum at endless-sphere.com praises them highly.
I've purchased from nycewheels.com (Quando II) and experienced quick shipping and a reasonable exchange of a damaged battery.
I also purchased from itselectric.ca (Wilderness kit) and found their prices reasonable (lower than most for this kit) with quick shipping and quick to answer inquirys.